1. Technical Field
The present invention relates to a liquid dispensing apparatus.
2. Related Art
Liquid dispensing apparatuses thus far known include an ink jet image forming apparatus configured to dispense ink, an example of the liquid, from a head to thereby form an image. Many of such ink jet image forming apparatuses include an ink supply path through which the ink is supplied from an ink tank in which the ink is stored to the head that dispenses the ink, for example as disclosed in JP-A-2007-160749. For example, the ink jet printing apparatuses for industrial use, particularly large-scale printing apparatus designed for large sheet printing, consume a large amount of ink and therefore generally an ink tank capable of storing a large amount of ink is provided separately from the head, and a tubular ink supply path is arranged between the head and the ink tank.
In such ink jet image forming apparatuses, the ink supply path may include a section where there is a level difference in a vertical direction. In the case of the ink jet printing apparatuses for industrial use in particular, the level difference in the vertical direction often exceeds 100 mm, and in the large-scale printing apparatuses the level difference may even exceed 300 mm.
Now, in some types of ink used in the ink jet image forming apparatuses, a pigment component contained in the ink is prone to precipitate (hereinafter the precipitation of the pigment component in the ink will be simply referred to as precipitation of ink), and therefore a difference in ink density is prone to be produced in the ink. For example, white ink is a kind of such sedimentary ink. The precipitation of the ink more actively takes place in the section of the ink supply path having a level difference, and in case that an image is outputted with the ink in which the precipitation is prominent, the density of the outputted image largely deviates from the expectation thereby significantly degrading the picture quality. Such a drawback is especially critical with the ink jet printing apparatuses in which the ink supply path has a large level difference in the vertical direction.
One of the measures to suppress the precipitation of the ink to thereby homogenize ink density is forming some stepped portions in the section of the ink supply path where there is a level difference. By forming the stepped portions, locations where the precipitation of the ink is relatively more active and locations where the precipitation of the ink is relatively less active are dispersed in a plurality of locations, which suppresses appearance of an extreme difference in ink density.
However, although appearance of an extreme difference in ink density can be suppressed by forming the stepped portions, at some locations, for example a bottom portion or a corner portion of the stepped portion, the precipitation of the ink still takes place. Accordingly, a certain extent of difference in ink density still remains, which may affect the picture quality. Thus, from the viewpoint of improvement of the picture quality, forming the stepped portions in the sections where there is a level difference is insufficient for homogenizing the ink density, and therefore a more effective measure for homogenizing the ink density is being sought for.